Conversion of hydrocarbons



Oct. 31, 1939. c. HUFF CONVERSION OF HYDROCARBONS TORNEY INVENTOR LY MANC. HUFF Filed Nov. 39, 1936 2 Sheets-Sheet l Oct. 31, 1939. L. c. HUFFCONVERSION OF HYDROGARBONS Filed Nov. 30, 1936 2 Sheets-Sheet 2 n0-muzuuwm INVENTOR Patented Oct. 31, 1939 UNITED STATES PATENT OFFICECONVERSION OF HYDROCARBONS Application November 30, 1936, Serial No.113,424

17 Claims.

This invention particularly refers to an improved process for theselective pyrolytic conver-- sion of four separate streams ofhydrocarbon oils ranging in characteristics from low-boiling distillatesuch as gasoline, heavy gasoline fractions,

naphtha pressure distillate and the like to highboiling residual oils,the light distillate stream being subjected to reforming conditions, thehighboiling residual oils being quickly heated to a high crackingtemperature and thence reduced to coke in a continuous operation whilethe two intermediate streams are each subjected to independentlycontrolled conversion conditions of cracking temperature andsuperatmospheric pressure.

1?; In this invention the four selective cracking stages are correlatedin an interdependent and cooperative manner so as to produce, as finalproducts of the process, high yields of good qual-' ity gasoline andminor yields of relatively dry 2 0 coke and gas of relatively higholefin content.

One of the features of the invention resides in the flexibility ofoperation which it provides,

making the system adaptable to the treatment of a wide range of chargingstocks as well as to 25, the simultaneous treatment of a plurality ofcharging stocks of different characteristics. The process also possessesconsiderable flexibility with respect to the characteristics of theproducts and may, when desired, be operated for the production of eitherrelatively dry coke or good quality fuel oil as the final residualproduct of the process or for the simultaneous production of both cokeand fuel oil residue.

While considerable importance is attached to the novel cooperativerelations between the various steps of the process which combine to makea new, highly desirable and advantageous cracking unit, many of itsnovel features are also adaptable to use in other combinations and inother 40; types of cracking systems and it is therefore not desired tolimit the invention to the entire combination and sequence of steps whch make up.

the unified, system herein illustrated and described as the specificembodiment of the invention.

considered new, per se, comprises introducing residual liquid resultingfrom a separate cracking One of the features of the invention which isoperation, quickly heating these high-boiling residual liquids to arelatively high cracking temperature in a heating coil without allowingthem sufficient time in the heating coil at the high conversiontemperature employed to permit any substantial formation and depositionof coke therein, introducing the highly heated residual oils into thecoking zone wherein they are reduced to substantially dry coke andsupplying the evolved vapors to said separating zone. Although in thespecific embodiment of the invention hereinafter illustrated anddescribed, the residual liquid supplied to the low-pressure vaporizingand separating step comprises residual oil resulting from the pyrolyticconversion of lower boiling oils in separate cracking stages of thecracking system, this particular feature of the invention is not solimited since it may include as the oil supplied to the vaporizing andseparating step not only cracked residue in heated state but any desiredhydrocarbon oil of high-boiling characteristics or relatively wideboiling range from within the system or from an external source. It maybe introduced intothe vaporizing and separating zone either in preheatedstate or otherwise, as desired, but preferably is supplied thereto at atemperature below that at which any appreciable cracking thereof willoccur under the conditions employed in the vaporizing and separatingzone but at a sufficiently high temperature so that by commingling withthe vaporous products from the coking operation it is subjected toappreciable vaporization.

Another important feature of the invention resides in the cooperativerelation between the reforming and coking stages of the system whereby aregulated portion of the highly heated products from the heating coil ofthe reforming step are commingled with the residual materials undergoingcoking to assist the coking operation while the remainder of the highlyheated reformed products are cooled sufficiently to prevent anyexcessive further cracking and polymerization thereof, undesirablehigh-boiling polymers and cracked products separated from the partiallycooled materials and returned to the coking stepv Another feature of theinvention comprises subjecting vaporous products of the desiredendboiling point from the fractionating step of a cracking operation tofurther fractionation whereby they are separated into fractionatedvapors within the boiling range of the desired gasoline product of theprocess, which is recovered therefrom by condensation, and higherboiling components including high-boiling gasoline fractions ofunsatisfactory antiknock value, supplying regulated quantities of saidhigher boiling components to a heating coil wherein they are subjectedto reforming conditions of cracking temperature and substantialsuperatmospheric pressure, cooling at least a portion of the highlyheated products discharged from the heating coil to a sufiiciently lowtemperature to prevent their appreciable continued cracking, subjectingthe vaporous components of the partially cooled products to separatefractionation, subjecting fractionated vapors of the desired end-boilingpoint, comprising materials of gasoline boiling range from the lastmentioned fractionating step, to condensation, recovering the resultingdistillate, returning reflux condensate formed in the last mentionedfractionating step to the first fractionating step wherefrom thevaporous conver- -sion products subjected to said further fractionationare derived and supplying reflux condensate from said firstfractionating step to the cracking step wherein the first mentionedvaporous conversion products are produced.

Other advantageous features of the invention which are novel inthemselves and/or in combination with various other features of theprocess will be apparent to those familiar with the cracking art byreference to the accompanying diagrammatic drawings and the subsequentdescription thereof.

One specific embodiment of the invention comprises subjecting relativelylight and relatively heavy hydrocarbon oil cracking stocks each to asuitable independently controlled cracking temperature at substantialsuperatmospheric pressure in independently controlled light oil andheavy oil cracking coils and an enlarged reaction zone maintained atsubstantial superatmospheric pressure to which heated products from bothcracking operations are supplied, separating the resulting vaporous andresidual liquid conversion products and subjecting the latter to furthervaporization at substantially reduced pressure, heating the remainingresidual liquid to a high cracking temperature at superatmosphericpressure in another independently controlled heating coil, introducingthe heated materials into an enlarged coking zone wherein theirhigh-boiling components are reduced to substantially dry coke,separately heating another hydrocarbon oil of lower boilingcharacteristics than that supplied to said light oil cracking step toreforming con ditions of cracking temperature and superatmosphericpressure in another independently controlled heating coil, introducing aregulated portion of the heated products from the reforming step intothe coking zone to commingle therein with the materials undergoingcoking and assist the coking operation, cooling the remaining portion ofsaid heated products from the reforming step sufficiently to preventtheir excessive further conversion, separating from the par tiallycooled materials high-boiling non-vaporous components, returning thelatter to the heating coil to which said residual liquid is suppiled,subjecting the total vaporous conversion prod ucts of the process andhydrocarbon oil charging stock for the process to fractionation for theformation of light oil and heavy oil cracking stocks, supplying thesame, respectively, to the light oil and heavy oil cracking steps,subjecting fractionated vapors of the desired end-boiling point tocondensation and recovering the resulting distillate.

Another specific embodiment of the invention comprises subjecting an oilof relatively high boiling characteristics recovered from within thesystem to cracking temperature at superatmospheric pressure in a heatingcoil, simultaneously subjecting another oil of lower boilingcharacteristics to independently controlled conditions of pyrolyticconversion in a separate heating coil, introducing heated products fromboth heating coils into a reaction chamber also maintained atsubstantial superatmospheric pressure wherein they are subjected toappreciable continued cracking, withdrawing both vaporous and liquidconversion products in commingled state from the reaction chamber andintroducing the same into a reduced pressure vaporizing and separatingchamber wherein the liquid products are sub-- jected to appreciablevaporization and the residual liquid is separated from the vapors,withdrawing the vaporous products from the vaporizing and separatingchamber and subjecting the same to fractionation in commingled statewith hydrocarbon oil charging stock for the process whereby thecomponents of the commingled materials boiling above the range of thedesired light distillate product of this stage of the system arecondensed as reflux condensate and separated into selected relativelylow-boiling and high-boiling fractions, supplying said high-boilingfractions to the first mentioned heating coil for cracking, supplyingsaid low-boiling fractions to said separate heating coil for cracking,removing from the fractionator vapors of the desired end-boiling point,including substantially all of the components of the oil supplied to thefractionator boiling within the range of gasoline, subjecting aregulated portion of said fractionated vapors to partial condensation,returning regulated quantities of the resulting distillate to the upperportion of the fractionator as a cooling and refluxing medium,subjecting the remaining portion of said fractionated vapors to furtherfractionation whereby they are separated into com ponents boiling withinthe range of the desired gasoline product of this stage of the systemand higher boiling components, which latter are condensed by saidfurther fractionation, removing said low-boiling components from thelast mentioned fractionating zone, subjecting the same to partialcondensation, returning regulated quantities of the resulting distillateto the last mentioned fractionating zone as a cooling and refluxingmedium, subjecting the uncondensed materials and any excess distillatefrom both of said partial condensation steps to further cooling andcondensation, recovering and separating the resulting distillate anduncondensed gases, withdrawing said condensate formed in the lastmentioned fractionating zone therefrom, returning a regulated portionthereof to the first mentioned fractionating zone, supplying anotherportion of the condensate in regulated quantities to a separate heatingcoil wherein it is subjected to reforming conditions of crackingtemperature and substantial superatmospheric pressure, introducingregulated quantities of the resulting highly heated products into acoking zone wherein they commingle with heated residual liquids suppliedthereto from within the system, as subsequently described, whereby toassist reduction of said residual liquids to coke, cooling the remainingpor tion of the highly heated products from the last mentioned heatingcoil sufiiciently to prevent their excessive further cracking,introducing the partially cooled materials and vaporous products removedfrom the coking zone into another separating chamber wherein thehigh-boiling nonvaporous components of the materials supplied theretoare separated from the vapors, removing said residual liquid from thefirst mentioned vaporizing and separating chamber and supplying at leasta regulated portion thereof to the last mentioned separating chamber,withdrawing the resultant commingled high-boiling liquids from the lastmentioned separating chamber, supplying the same to another separateheating coil wherein they are quickly heated to a relatively highcracking temperature, introducing the heated materials from the lastmentioned heating coil into thecoking zone wherein theirhighboilingcornponents are reduced to substantially dry coke, subjectingvaporous products from the last mentioned separating chamber tofractionation in another fractionating zone for the formation of refluxcondensate, passing regulated quantities of the last mentioned refluxcondensate in indirect heat exchange with said condensate supplied tothe reforming coil whereby to supply additional heat to the latter,prior to its introduction into the reforming coil and whereby topartially cool said reflux condensate, returning reflux condensate fromthe last men'- tioned fractionating zone to the first mentionedfractionating zone, subjecting fractionated vapor s'of the desiredend-boiling point from sa d last mentioned fractionating zone to partialcondensation, returning regulated quantities of the resulting distillateto the upper portion of said last mentioned fractionating zone as acooling and refluxing medium, subjecting uncondensed 1; materials andany excess distillate from the last drawings.

Referring to the drawings, relatively high-boil ing charging stockorcharging stock of relatively wideboiling range is suppliedthrough-line I and valve 2 to pump 3 wherefrom it is directedthroug h,line t and may be supplied through valve 5 in this line to fractionator5.

Low-boiling charging stock such as distillate, naphtha, gasoline or thelike is supplied through line I and valve 8 to pump '9 wherefrom itisdi- 1 rected through line H), valve ll, heat exchanger l2, line l3 andvalve I 4 into fractionator '6.

The oil passed through heat exchanger I2 is indirectly contacted withrelatively hot vaporous products undergoing fractionation in this zonewhereby it is preheated and serves to partially cool the vapors andassist their vaporization.

The oils supplied, as described, through lines 4 and it intofractionator 6 directly comming'le in this zone with the hot vaporousproducts undergoing fractionation whereby said oils are subjected toappreciable vaporization and to fraction-' ation, together with thevaporous conversion products and also serve to partially cool the vaporsand assist fractionation in this zone. The condensate removed from thevaporous products by fractionation in fractionator 6 includingcomponents of both in the charging stock and the vaporo us conversionproducts suppl ed to this zone boiling above'the range of gasoline isseparated into light andheavy fractions of selected boilingcharacteristics. The high-boiling fractions of heavy reflux condensateis withdrawn from the lower portion of the fractionator and directedthrough line l5 and valve Hi to pump I! by means of which it is fedthrough line it and valve 19 to cracking coil 20.

Coil 29 is located within a suitable furnace 2| and the oil passingthrough the coil is heated to the desired cracking temperature,preferably at a substantial superatmospheric pressure. The heatedproducts are discharged from coil 20 through line 2?. and valve 23 intoreaction chamber24, preferably entering the upper portion of this zoneand being directed by means of a suitable spreader flange or sprayarrangement such as indicated, for example, at 25 against the innersurface of the walls of the chamber.

The light or low-boiling reflux condensate formed in fractionator 5 iswithdrawn from a suitable intermediate point in the fractionator anddirected through line 26 and valve 2! to pump 28 by means of which it isdirected through line 29 and valve 30 into cracking coil 3|.

A suitable furnace 32 supplies the required heat to the oilpassingthrough coil 3i to subject the same to the desired cracking temperaturewhich is preferably higher thanthat employed in heating coil 20,preferably at a substantial superatmospheric pressure. The heatedproducts are discharged from coil 3! through line 33 and may bedirected, all or in part, through line 34 and valve 35 in reactionchamber 26.

Chamber 24 is also preferably maintained at a substantialsuperatmospheric pressure and, although" not indicated in the drawings,is preferably well insulated to prevent the excessive loss of heattherefrom by radiation. The heated products supplied to chamber 24 arethereby subjected to appreciable continued conversion time in this zoneand both vaporous and liquid conversion products are withdrawn incommingled state from'the lower portion of the chamber and drectedthrough line 36 and valve3l into vaporizing chamber 38.

Chamber 38 is preferably operated at a substantially reduced pressurerelative to that employed inthe reaction chamber by means of whichappreciable further vaporization of the liquid products supplied to thiszone is accomplished. The oils remaining unvaporized in chamber 38 arewithdrawn from the lower portion of this zone through line 39 and valveMl to pump 4! wherefrom they are directed through line 42, valve 43 andline 44 into the lower portion of column 45, the purpose of which willbe later described.

- Vaporous products are directed from the upper portion of chamber 38through line 45 and valve 41 into fractionator 6 wherein they comminglewith the charging stock supplied to this zone,

as previously described, and are subjected therewith to -fractionationfor the formation of said light and heavy reflux condensates and for therecovery therefrom of low-boiling fractions comprising materials withinthe boiling range of gasoline.

Fractionated vapors of the desired end-boiling point comprisingmaterials within the boiling range of the desired final gasoline productof the process as well as, when desired, somewhat higher boilingfractions, are removed from the upper portion of fractionator 6 throughline 48 and these products are divided into two streams, one ofwhichpasses from line 48 through line 50 and valve 5| into fractionator 52for separation therein'into light and heavy fractions, as will be laterdescribed, while the other stream passes through valve G9 in line 68 tocondensation and cooling in condenser 53. The resulting distillate anduncondensed materials pass through line 54 and valve 55 into accumulator56 and distillate is returned from this zone by means of line 51, valveE8, pump 55, line 60 and valve Bl to the upper portion of fractionator 6wherein it serves as a cooling and refluxing medium. Gas and uncondensedvapors are directed from accumulator 56 through line E2 and valve 63 tosub-coolers 64, the purpose of which will be later described.

The vapors supplied, as previously described, from fractionator 6 tofractionator 52 are subjected to additional fractionation in the latterzone whereby their components, within the boiling range of gasoline, ormore particularly lowboiling gasoline fractions, are recovered fromtheir higher boiling components. The low boiling fractions are removedfrom the upper portion of fractionator 52 and directed through line 65and valve 66 to cooling and partial condensation in condenser 67. Theresulting distillate and uncondensed vapors and gases are directedthrough line 68 and valve 69 to accumulator l0. Distillate is returnedfrom accumulator Til by means of line H, valve l2, pump 13, line H andvalve 15 to the upper portion of fractionator 52 to serve as a coolingand refluxing medium in this zone. Uncondensed vapors and gases as wellas any condensate recovered in receiver '30 in excess of that requiredas a cooling and refluxing medium are directed through line 16 and valve11 into line 62 wherein they commingle with similar materials fromreceiver 56, being directed therewith, as previously described, tosub-coolers 64.

The materials thus supplied to sub-coolers 64 comprise gaseous productsof the cracking operation, previously described, and other components ofthe vaporous products from fractionator 6 which boil within the range ofgasoline and are of satisfactory antiknock value. The sub-coolingaccomplished in zone 54 serves to effect separation in receiver to whichthe sub-cooled products are supplied through line 18 and valve 19 ofnormally condensable components from uncondensed gases. The formercomprising the distillate collected in receiver 80 is withdrawntherefrom as the final product of the process through line 3! and valve82 to storage or elsewhere, as desired. The normally gaseous productsare released from receiver 80 through line 83 and valve 8 3.

High-boiling components of the vaporous products supplied tofractionator 52 which are condensed in this zone and which comprise, forexample, high-boiling motor fuel fractions of unsatisfactory antiknockvalue and which may include, when desired, somewhat higher boilingmaterials such as heavy naphtha fractions, pressure distillate bottomsor the like are withdrawn from the lower portion of fractionator 52 andmay be directed through line 85 and valve 86 to pump il by means ofwhich they are supplied, as will be later described, to furthertreatment within the system for the improvement of their motor fuelcharacteristics, particularly with respect to antiknock value. It isalso within the scope of the invention to remove a regulated portion orall of the material withdrawn from the bottom of fractionator 52 fromthe system. This is accomplished by diverting the same from a linethrough line 38, line 8d and valve 98 to cooler sl wher-efrom the cooledproduct is discharged through line 92, line 93 and valve 95 to storageor to any desired further treatment. This method of operation isparticularly advantageous in case the high-boiling components of thegasoline product of this state of the system are of satisfactoryantiknock value but may be advantageously subjected to differenttreatment than the low-boiling gasoline fractions such as, for example,chemical treatment for the reduction of sulphur content and the like,clay treatment for the reduction of gums or in case the low-boilingfractions require stabilization and it is not necessary to subject thehigh-boiling fractions to such treatment.

It is also within the scope of the invention to utilize regulatedquantities of the oil withdrawn from the lower portion of fractionator52 as a cooling and refluxing medium in fractionator 6, in which caseoil from the bottom of fractionator 52 may be passed through valve 96 inline 88 to pump 91 by means of which it is supplied through h line 98and valve 99 to heat exchanger l2 and thence through line 13 and valvel4 into fractionator 6.

Provision is also made for returning a regulated portion or all of thecooled oil from cooler 9! to fractionator 6 by means of directing thesame through valve Hill in line 92 into line 88 and thence in the mannerpreviously described, to pump 9'5, heat exchanger [2 and fractionator 5.

The invention also contemplates returning dis- 1;

tillate from receiver H! to fractionator 6 by diverting regulatedquantities thereof from line 14 through line lei and valve H32 into line98 and thence, as previously described, through heat exchanger !2 intofractionator 6.

Provision is also made for returning regulated quantities of the bottomsfrom fractionator 52 to the lower portion of this zone in order toassist cooling therein by means of diverting the oil preferably after itis passed through cooler 9|, as previously described, from line 98through line H13 and valve I04 into the lower portion of fractionator52.

Line I05 and valve I06 communicating with line 88 is provided for thepurpose of supplying distillate from an external source to pump 9! andthence either to the lower portion of fractionator 52 or through heatexchanger l2 to fractionator 6, in the manner previously described. Thisadditional cooling medium may comprise any desired oil from an externalsource which will not contaminate the products of the process with whichit is commingled or it may comprise oil from the lower portion offractionator previously supplied to storage, in the manner alreadyindicated.

When the material withdrawn from the lower portion of fractionator 52comprises gasoline fractions and/or somewhat higher boiling materials ofthe nature previously mentioned which may be advantageously subjected toadditional cracking or reforming to produce additional yields ofgasoline of good antiknock value, a portion or all of this material issupplied, as previously described, to pump 8'! wherefrom it is fedthrough line I01 and valve I03 and this material may either be directed,all or in part, through valve H19 in line H]? to cracking or reformingcoil H0 or it may first be preheated by diverting it. all or in part,from line Hi! through line ill, through branch lines H2 controlled byvalves H3 into heat exchanger ll l wherein it passes in indirect heatexchange with relatively hot intermediate products of the processsupplied to the heat exchanger, as will be later described, and

high superatmospheric pressure.

wherefrom the preheated oil is directedthrough, lines H5 and valves II6into line H1 and thence through line I61 to coil H0.

Coil I I0 is located within a suitable furnace I I8 by means of whichsufficient heat is supplied to, the oil passing therethrough to subjectit to the desired conversion conditions of relatively high crackingtemperature, preferably at a relatively Preferably the oil passingthrough coil I I 0 is subjected to a more prolonged conversion time thanthat employed for the higher boiling oils separately subjected tocracking within the system and for this purpose, although a conventionalheating coil and furnace are shown in the drawings, any of the wellknown types of heaters wherein a soaking section is pro vided ispreferably employed. I

The highly heated products are discharged from heating coil IIO throughline H9 and maybe directed, all or in part, through valve I26 in thisline to fractionator I2I or a portion or all of these materials may bediverted from line I I9 and supplied through line I22, valve I23, lineI24, valve I and line I26 into fractionator 6 wherein they comminglewith the vaporous products supplied to this zone, as previouslydescribed,

from chamber 38 and are subjected to fractionation therewith, in themanner previously described.

When products from coil H6 are supplied, as described, to fractionatorI2l they are separately subjected to fractionation in this zone andseparated into components boiling within and above the boiling range ofthe desired final gasoline product. The high-boiling fractions,including any residual liquid conversion products and/or heavy polymers,are withdrawn from the lower portion of 'fractionator I2I through lineI21 and may, when desired, be removed, all or in part, from the systemthrough line I28 and valve I29 to cooling and storage or elsewhere, asdesired, or this material may be directed, all or in part, through valveI30 in line I21 to pump I3I by means of which it is directedthrough'line I32, valve I33 and line 44 into separating andfractionating column 45 wherein it is subjected to furthertreatment, aswill belater described.

When desired, intermediate fractions of the materials supplied tofractionator I2I comprising their components boiling above the range ofthe desired gasoline product and below the range of the relatively heavyliquids which it is desired to subject to further treatment in column 45may be removed from a suitable intermediate point in fractionator I2Iand directed through line I34 and valve I35 to pump I36 by means ofwhich they are supplied through line I31 and valve I33 to cooler I39 andthence through line I46, valve I 4|, line I 24, valve I25 and line I26into trac tionat'or 6 to commingle therein with the othermate'rialssupplied to this zone, as previously de-' scribed, and be subjected tofractionation therewith,

actionated vapors of the desired end-boiling point comprising normallygaseous products and materials within the boiling range of thedesiredgasoline product are directed from the upper serve as a coolingand refluxing medium in this zone. vAny additional distillate collectedin receiver I49 is directed together with uncondensedvapors and gasesfrom this zone through line I55, valve I56 and line I51 to sub-coolerI56 wherein additional cooling to effect condensation of the vaporousproducts within the boiling range of the desired gasoline product isaccomplished. The resulting distillate and uncondensed gases passthrough line I59 and valve I60 to receiver I6I wherein separation of thedistillate and gases is accomplished. Gaseous products are released fromreceiver I6I through line I62 and valve I63 and distillate is withdrawnfrom this zone through line 864 and valve I65 to storage or to anydesired further treatment.

The heavy oils supplied to column 45 from chamber 38 and when thismethod of operation is employed from the lower portion of fractionatorI2I may be subjected to additional vaporization in the lower portion ofcolumn 45 for the recovery of desirable low-boiling fractions therefrom. The remaining residual liquids are removed from the lower portionof column 45 and directed through line I66 and valve I61 to pump I68 bymeans of which they are supplied through line I69 and valve I16 tofurther treatment in heating coil I1I.

A suitable furnace I12 supplies the required heat .to the heavy oilspassing through coil I1I to quickly heat the same preferably to arelatively high temperature sufficient to induce or assist their,subsequent reduction to coke without allowing the oil to remain in theheating coil and communicating lines for a sufiicient length of time'topermit excessive coke formation and deposition therein. The heatedresidual oils are discharged from heating coil I1I through line I13 andvalve I14 and are split by means of stream-divider I15 into two streamsof substantially equal volume which are directed through the respectivelines I16 and I16 into coking chambers I11 and I11. The heated residualoil may enter the coking chambers at any desired pointor plurality ofpoints therein, provision be-- ing madein the case here illustrated forsupplying the heated oil from line I16 through line I18 and valve I19into the upper portion of chamber I11 or through line I80 and valve I8Iinto the lower portion of the chamber While the stream of heated oilfrom line I16 may pass through line I18 and valve I19 into the upperportion of chamber I11 or throughline I80 and valve I8If into the lowerportion of the chamber or heated products may be supplied into both theupper and lower portions of the coking chambers by means of the linesand valves described.

The heated residual oils supplied to the coking chambers are reducedtherein to substantially dry coke and preferably in order to assist thecoking operation and to reduce the volatility of the coke producedregulated quantities of the highly heated relatively low-boiling oilsfrom coil 3| and/or from coil IIO may be introduced into the cokingzones wherein they preferably come into direct contact with thematerials undergoing coking therein and pass upwardly therethrough tosupply additonal heat to the materials undergoing coking and furtherassist the coking operation by their partial pressure effect. Provisionis made for diverting from line 33 a regulated portion or all of theheated products discharged from coil 3| into line I82 wherefrom they aredirected through Valve I83 in this line and through lines I84 and I84controlled, respectively, by valves I85 and I85 into the lower portionof coking chambers IT! and "1, respectively. Provision is also made inthe case here illustrated, for diverting a regulated portion or all ofthe highly heated products discharged from coil 8 I0 through line I 59into line I86 and thence through valve H31 in this line into line I83and thence, as previously described, into the lower portion of cokingchambers IT! and Ill.

The coke produced in the coking chambers may be allowed to accumulatetherein until they are substantially filled or until their operation iscompleted for any other reason, following which the chambers may becleaned in any well known manner, not illustrated, and prepared forfurther operation.

It will, of course, be understood that although two coking chambers areshown in the drawings, a single coking zone or more than two such zonesmay be employed, when desired. When a plurality of coking zones isutilized either alternate or simultaneous operation thereof may beemployed, alternate operation being preferred in order that the cokingstage in common with the rest of the system may be operatedcontinuously.

The provisions for introducing heated products from coil BI and/or coilIII] into the coking zone, in addition to assisting the coking operationin the manner above described, permits preheating the coking chambersbefore the residual oil to be coked is supplied thereto.

Coking chambers IT! and III are provided, respectively, with drain-linesI88 and I88 having the respective valves I89 and I89. These lines andvalves may also be utilized as a means of introducing suitable coolingmaterials such as Water, steam or the like into the mass of cokeaccumulated in the chambers after their operation is completed andpreferably after they have been isolated from the system in order tohasten cooling and facilitate removal of the coke.

Vaporous products are withdrawn from the upper portion of chambers I11and H1 through the respective lines IQ'ii and I90 having the respectiveshut-off valves I9I and I9I' through a stream uniting valve I92 intoline I93 wherefrom they are directed into the lower portion of column45.

The materials supplied to column 45 are separated by vaporization andfractionation into three components, the heavy components comprisingmaterials withdrawn from the lower por-- tion of the column andreturned, as previously described, to coil I'll include any heavyresidual liquids, tars and the like of high coke-forming characteristicscarried over with the vapors from the coking zone and also includenon-vaporous residual components of the liquid products supplied tocolumn 15, as previously described, from chamber 35 and fractionatorI2I.

The intermedate components of the materials suppled to column 45comprise the fractions of these materials, suitable for further crackingwhich boil above the end-point of the desired final light distillateproduct of this stage of the system and below the initial boiling pointof the materials returned to heating coil I'II. These intermediatefractions are withdrawn from a suitable intermediate point in column 45and are directed through line I94 and valve I95 to pump I55 wherefromthey are fed through line I91 and may be directed, all or in part,through line I26 and valves I98 and I99 into fractionator 6 to commingletherein with the other materials undergoing vaporization andfractionation in this zone and be subjected to fractionation therewith.

Preferably, however, in order to recover useful heat from theintermediate products thus withdrawn from column 45 and to partiallycool the same so that they may, in turn, partially cool and assistfractionation of the vaporous products in fractonator 5 when returned tothis zone, all or a portion of the intermediate products may, whendesired, be directed from line I91 through line 280 and through branchlines 2M containing valves 202 into and through heat exchanger II4wherein they pass in indirect heat exchange with the relatively cool oilpassing from the lower portion of fractionator 52 to coil H8, in themanner previously described. The thus cooled intermediate fractions passfrom heat exchanger II4 through lines 203 containing valves 204 intoline 205 from which they are directed into line I26 and thence tofractionator 6.

Provision is also made for supplying a regulated portion or all of theintermediate products from column 45 to further cracking in coil III] bymeans of diverting the same from line 200 through line 256 and valve 25?into line 10'! and thence to heating coil III]. This method of operationpermits selectively cracking the intermediate products of the cokingstage of the system separate from the light and heavy fractions of thereflux condensate produced in the first described cracking operationsand is particularly desirable in case the gasoline produced in said 3first mentioned cracking operations is of satisfactory antiknock valueand the high-boiling fractions of said gasoline do not require reformingin heating coil I It. However, it is entirely within the scope of theinvention to supply both 1 relatively light distillate, including anyheavy gasoline fractions, from fractionator 52 and higher boilingintermediate fractions from column 45 both to heating coil H6 andsubject the commingled materials to relatively severe crackingconditions in this zone.

Provision is made in the case here illustrated, for supplying aregulated portion or all of the products discharged from heating coil IID to column 45, when desired, this being accomplished by means of line238 containing valve 209 which communicated with line H9 and with thelower portion of column 45.

Provision is also made, in the case here illustrated, for supplyingregulated portion or all of the relatively heavy charging stock tocolumn 45 by diverting said charging stock from line 4 through line areand valve 2II wherefrom it may be directed through either or both of thebranch lines H2 and 2I3 containing valves 2I4 and 2I5, respectively,into the respective lines 2 I6 and 2I'I and thence into column 45. Line2I6 enters column 45 below the point at which intermediate fractions arewithdrawn from this zone and line 2H enters the column above this point.

Provision is also made for returning intermediate fractions withdrawnfrom column 45 bad" to this zone in regulated quantities preferablyafter being cooled in heat exchanger II4 whereby to serve as a coolingand fractionating medium in column 45. This is accomplished by means ofvalves 2I8 and 2I9 in the respective lines ZIG and 2II, each of whichcommunicate with line I26 and with column 45.

The overhead vaporous product from column 45 comprising materials withinthe boiling range of the final gasoline product of this stage of theprocess are directed from the upper portion of column 45 through line220 and valve 22I to condenser 222 wherein they are subjected to coolingand partial condensation. The resulting distillate and uncondensedvapors and gases pass through line 223 and valve 224 into accumulator225 wherefrom regulated quantities of the distillate may be recirculatedby means'of line 229, valve 221, pump 228, line 229 and valve 230' backto the upper portion ofcolumn to serve as a cooling and refluxing mediumin this zone. Uncondensed vapors and gaseous products pass together withany excess of condensate recovered in accumulator 225 from this zonethrough line 23I and valve 232 into line I51 wherein they commingle withsimilar materials from accumulator I 49, passing therewith to furthercooling and condensation in sub-cooler I58 and thence toseparation inreceiver Iiii, as previously described.

In addition to the methods and means of cooling and heat exchange,previously described, provision is made for controlled cooling to anydesired degree of various relatively hot intermediate products of theprocess at various points in the system by directly commingling the samewith cooler intermediate products. For example, it may be desirable topartially cool the relatively hot products supplied fromv coil 3| tochamber 24 and/or to cool the conversion products from the lower portionof chamber 24. This is accomplished, in the case here illustrated, bydiverting regulated quantities o f-the low-boiling reflux condensateremoved from fractionator 6 from line 25 through line 233 and valve 234to pump 235 wherefrom it is directed through line 236 and may pass, allor in part, through valve 231 in this line into line 238 and thencethrough lines 239 and 249 into line 34, entering line 34 in the casehere illustrated, at valve 35 in this line through valve 24I in line240. Preferably, however, a portion or all of the light reflux thusdiverted from line 21 is passed through cooler 236 before it is utilizedas a cooling medium, this being accomplished by means of diverting thesame from line 236 through line 242 and valve 243 into cooler 244 andthence through line 245 and valve 245 into line 238. This low-boilingreflux condensate with or without first passing through cooler 244 mayalso be introducedwhen desired, into the lower portion of chamber 24through line 241 and valve 248 and it may also be utilized, whendesired, as a means of partially cooling the hot products dischargedfrom coil I1 I by diverting it from line 239 through line 249 and valve254 into line 25I and thence through valve 252 into line I13. Provisionis also made in the case here illustrated, for introducing light refluxmingles with the intermediate fractions withdrawn from column 45 and issubjected to further treatment therewith and/or for passing said lightreflux in regulated quantities through valve 255 in line 25I into lineI31 wherein it commingles with the intermediate fractions withdrawn fromfractionator I2I and is subjected to further treatment therewith.

It is also often desirable to partially cool the highly heated productsdischarged from coil Ill], particularly in case a portion or all ofthese materials are supplied to column 45 and/or to fractionator I2I.The cooling medium utilized ,for this purpose, in the case hereillustrated, comprises a selected low-boiling fraction of the vaporousproducts undergoing fractionation in column 45. This selectedlow-boiling fraction is withdrawn from a suitable point. in the upperportion of column 45 and directed through line 256 and valve 251 to pump258 wherefrom it is directed through line 259 and may pass thenceeither, all or in part, through cooler 269 by means of lines 26l and263' controlled by the respective valves 262cand 264 or directly fromline 259 through line 265 and valve 269 into line 241 wherefrom it isintroduced into line H9 commingling therein with the heated productssupplied from coil Ill) to column 45 and/or to fractionator I2I.

Provision is also made for partially cooling the vaporous productswithdrawn from the coking zone, particularly for the purpose ofpreventing the formation and accumulation of coke deposits in this lineand in the valves interposed therein. Provision is therefore made forintroducing suitable'cooling oil into valves HM and I9I' or intothe'streams of vaporous products in lines I90 and I99 ahead of thesevalues, this being accomplished by means of line 268 and branch lines259 controlled by valves 210. The cooling oil employed for this purposemay comprise, for example, regulated portions of the condensate fromfractionator 45, preferably after it is passed through heat exchanger II4, although well known means for supplying this cooled condensate toline 2639 are not shown inthe drawing.

It will, of course, be understood that any other suitable coolingmaterial may be utilized at the points mentioned and that similar meansmay be employed for cooling at any other desired points in the system.

Provision is also made for using steam, when desired, in fractionator tiand column 45 to which it may be supplied through the respective lines2H and 213 controlled, respectively, by valves 212 and 214' The steamthus utilized commingles with the steam undergoing fractionation,assisting their fractionation. and exerting a refining actionthereon.

In addition to the provisions comprising lines I28 and valve I29 forremoving condensate from fractionator [H as a final product of theprocess, any of the various other intermediate products of the systemmay be withdrawn therefrom in a similar manner. For example, a portionor all of the low-boiling reflux condensate from fractionator 6 may beremoved from the system by passing the same through valve 215 in line238, preferably after it has passed through cooler 244-. Intermediatecomponents of the materials supplied to column 45 may also be withdrawnfrom the system to cooling and storage or elsewhere, as desired, bydiverting the same from line I 23 through line 216 controlled by valve211. The oils thus withdrawn from column 45, fractionators I 2| andfractionator B may comprise, for example, materials suitable as domesticfuel or as Diesel fuel and in accordance with the process of theinvention, regulated quantities of such materials may be produced tomeet market requirements in addition to producing good quality gasoline,liquid residue, coke and gas, the production of all of these materialsbeing correlated to suit the particular economic conditions. Under theconditions ordinarily prevailing in most localities,

The. heatingcoil to which heavy reflux condensate from the firstcracking step is supplied may employ an outlet conversion temperatureranging, for example, from 850 to 950 352, preferably with asuperatmospheric pressure at this point in the system of from 100 to 500pounds, or more, per sq. in. Substantially the same or a somewhat lowersuperatmospheric pressure is preferred in the succeeding reactionchamber and the communicating separating chamber may be mainained atsubstantially the same or preferably at a somewhat lowersuperatmospheric pressure than that employed in the reaction chamberranging, for example, from 200 pounds to 50 pounds, or thereabouts, persq. in. The fractionator to which vaporous products from said separatingchamber are supplied is preferably operated at substantially the samepressure as the separating chamber, although the pressure in thefractionator may be reduced, when desired. The heating coil to whichlow-boiling reflux condensate from the first cracking stage is suppliedmay employ an outlet conversion temperature ranging, for example, from900 to l000 F. and preferably a superatmospheric pressure ranging from200 to 800 pounds, or more, per sq. in. is employed at the outlet fromthis zone. When a secondary fractionator is employed in the firstcracking stage of the system the pressure employed therein may besubstantially equalized but, preferably, is substantially reducedrelative to that employed in the preceding iractionator, the preferredrange being from substantially atmospheric to 150 pounds, orthereabouts, per sq. in. superatmospheric pressure. The heating coil towhich the residual liquid to be coked is supplied preferably employs anoutlet conversion temperature ranging from 900 to 1000 F. with asuperatmospheric pressure at the outlet from this zone ranging from 50to 200 pounds, or thereabouts, per sq. in. The oil velocity and rate ofheating in this coil is such that the heavy residual liquid may beheated to a sufficiently high temperature to effect its subsequentreduction to coke without excessive coke formation and deposition in theheating coil and communicating lines. The coking chambers may beoperated at any desired pressure ranging from substantially atmosphericup to substantially the same pressure as that employed in the residualliquid heating coil. The separating and fractionating column to whichvaporous products from the coking zone are supplied is preferablyoperated at a substantially reduced pressure relative to that employedin the first separating chamber, this pressure ranging, for example,from substantially atmospheric up to substantially the same pressure asthat employed in the coking zone. When a separate heating coil isemployed for the reforming of high-boiling gasoline fractions from thesecon dary fractionator of the first cracking stage and/ or for crackingintermediate products from the separating and fractionating column towhich vaporous products from the coking zone are supplied, this coil mayutilize an outlet conversion temperature ranging, for example, from 900to 1050 F., preferably with a superatmospheric pressure at this point inthe system of from to 1000 pounds, or more, per sq. in. When all or aportion of the products from the last mentioned heating coil aresupplied to a separate fractionating column and/or to the sameseparating and fractionating column to which vaporous products irorn thecoking zone are supplied, they are preferably cooled, prior to theirintroduction thereto to a temperature of from 650 to 850 F., orthereabouts, this cooling normally being accomplished partially bypressure reduction and partially by the introduction of a suitablecooling medium into the stream of heated products. Said separatefractionating column, when employed, may be op erated at any desiredpressure ranging from sub stantially atmospheric up to substantially thesame as that employed at the outlet from the last mentioned heatingcoil, the preferred range being from 50 to 150 pounds, or thereabouts,per sq. in. superatmospheric pressure. The condensing, cooling andcollecting portions of the system may be operated at any desiredpressure ranging from substantially atmospheric up to substantially thesame as that employed in the preceding equipment.

As an example of one specific method of operation of the process, theconditions employed at various points in the system and the resultsobtained, two charging stocks are employed. The heavy charging stock,which comprises approxmately 50 per cent of the total, is a mixture clWest Texas and Mid-Continent topped crude of approximately 22 A. P. I.gravity having an initial boiling point of approximately 504 F. and anend-boiling point of approximately 750 F. The secondary charging stockcomprises pressure distillate from other cracking units having aninitial boiling point of approximately 102 F., an end-boiling point ofapproximately 640 F. and containing approximately 60 percent of materialboiling up to 400 F. Both of these charging stocks are supplied to theprimary fractionator of the first cracking stage Wherefrom the overheadvaporous stream, comprising the components of the pressure distillateand the components of the vaporous conversion products supplied to thiszone boiling up to approximately 400 F., are supplied, in part, to asecondary fractionator while another regulated quantity of theseoverhead vapors are subjected to partial condensation to form acondensate which is returned in regulated quantities to the primaryfractionator to serve as a cooling and refluxing medium. The higherboiling components of the materials supplied to the primary fractionatorare separated into relatively low-boiling and high-boiling refluxcondensates.

The high-boiling reflux condensate has an initial boiling point of about300 F'., contains approximately 40% of material boiling up to 600 andhas a gravity of approximately 15 A. P. I. This material is subjected tocracking in a heating coil, the oil entering the heating coil at atemperature of approximately 745 F. and a superatmospheric pressure ofapproximately 450 pounds per sq. in. and being discharged therefrom at atemperature of approximately 915 F. and a superatmospheric pressure ofapproximately 290 pounds per sq. in. The heated products from this coilare discharged into a reaction chamber which is maintained atsubstantially the same pressure at that employed at the outlet from theheating coil. Both vaporous and liquid conversion products are withdrawnfrom the lower portion of the reaction chamber in commingled state, andintroduced into a primary vaporizing and separating chamber at atemperature of approximately 865 F., this temperature being obtainedpartially by directly commingling a suitable cooling oil with theseproducts and partially by pressure reduction. The primary vaporizing andseparating chamber is operated at a superatmospheric pressm'e ofapproximately pounds per sq. in. and except for friction and loss ofpressure head this pressure is substantially equalized in the succeedingfractionating, condensing and collecting porend-boiling point ofapproximately 625 F. and a gravity of about 23 A. P. I. This material isdirected to a separate cracking coil, entering this zone at atemperature of approximately 680 F. and a superatmospheric pressure ofapproximately 760 pounds per sq. in. and being discharged therefrom at atemperature of approximately 955 F. and a superatmospheric pressure ofapproximately 290 pounds per sq. in.

Residual liquid from the primary vaporizing and separating chamber issupplied, as previously mentioned, to the separating and fractionatingcolumn to which vaporous products from the coking zone are supplied andthe nonvaporous residue from the latter zone is directed to a separateheating coil wherein it is quickly heated to an outlet conversiontemperature of approximately 950 F. at a superatmospheric pressure ofapproximately 115 pounds per sq. in. The heated products from this coilare introduced into alternately operated preconditioned coking chamberswherein their non-vaporous components are reduced to substantially drycoke. The coking chambers are operated at a superatmospheric pressure ofapproximately 115 pounds per sq. in. Vaporous products leave the cokingchambers at a temperature of approximately 885 F., are partially cooledby the introduction of a suitable cooling oil and thence introduced intosaid separating and fractionating column.

Materials within the boiling range of the desired gasoline product arerecovered from the fractionated vapors removed from the fractionatingzone of the coking stage, the vapors first being partially cooled andcondensed to form a condensate which is utilized as refluxing medium inthe fractionator and the remaining materials being subjected tosub-cooling and recovered as a final distillate and a gaseous product.

A relatively heavy condensate, comprising intermediate fractions of thematerials supplied to the separating and fractionating column of thecoking stage of the system and which have an initial boiling point ofapproximately 366 R, an end boiling point of about 650 F. and a gravityof about 19 A. P. I., is withdrawn from this zone and supplied to the.previously mentioned secondary fractionator of the first describedcracking stage of the system, wherefrom at least a substantial portionof these relatively high boilmately 790 pounds per sq. in. and aredischarged therefrom at a temperature of approximately 960 F. and asuperatmospheric pressure of approximately 130 pounds persq. in. Thetotal products discharged from the last mentioned heating coil arecooled partially by pressure reduction and partially by the injection ofa suitable cooling oil to a temperature of approximately 720 F. and areintroduced into a separate fractionating column maintained at asuperatmospheric pressure of approximately 120 pounds per sq. in. Themixture of reflux condensate, residual liquids and heavy polymerizationproducts having a boiling range of approximately 370 F. to 734 F. aredirected from the lower portion of this fractionating column to thelower portion of the separating and fractionating column of the cokingstage wherefrom their heavy non-vaporous components are supplied to theheating coil of the coking stage.

Intermediate components of the products from the reforming coil, havingan initial boiling point of about 166 F. and an end boiling point ofapproximately 616 F., are withdrawn as a sidestream from thefractionating column to which these materials are supplied and returnedto the previously mentioned secondary fractionator.

The overhead vaporous products from this secondary fractionator,including gasoline having an end boiling point of about 390 F. andnormally gaseous products, are partially cooled to form a refluxingmedium for the secondary fractionator and their remaining components aresubjected to further cooling, condensation and separation for I therecovery of a final gasoline product and gas.

Overhead vaporous products from the fractionating column of thereforming stage are subjected to' partial condensation for the recoveryof distil- A. P. I. gravity 61 Initial boiling point; F 88 End boilingpoint F 390 Antiknock value (motor method) 69 Vapor pressure (Reid) lbs.per sq. in 9 The coke produced amounted to approximately 37 pounds perbarrel of charging stock and was of a quality readily marketable asdomestic fuel.

The uncondensable gas produced amountedto approximately 385 cubic feetper barrel of charging stock and when subjected to absorption additional yields of high antiknock gasoline fractions may be recoveredtherefrom.

The only other products recovered from the system in the operation abovedescribed were approximately 12 percent, based on the total chargingstock, of two grades of good quality fuel, one of which, comprisingheavy fuel, was recovered as a portion of the residual liquid from theprimary vaporizing and reparating chamber and having an A. P. I. gravityof approximately 742 and a viscosity of approximately 60 seconds(Saybolt Furol) at 122 F. The other, comprising light fuel, wasrecovered as condensate resulting from passing vaporous products fromcoking chambers in operation through coking chambers about to be placedin operation in order to heat and precondition the latter. This producthas a gravity of approximately 21 A. P. I. and an end boiling point ofapproximately 640 F.

I claim as my invention:

1. In a process for the selective cracking of relatively low-boiling andhigh-boiling hydrocarbon oils wherein separate streams of hydrocarbonoils of different boiling range characteristics are each subjected toconversion conditions of cracking temperature and superatmosphericpressure in separately controlled cracking zones, the resultant heatedproducts commingled and subjected to appreciable continued cracking timeat the attained temperature of the mixture and at substantialsuperatmospheric pressure, the resultant conversion products supplied incommingled state to a zone of substantially reduced. pressure whereintheir vaporous and liquid components separate, the vapors subjected tofractionation whereby their components boiling above the desiredtemperature are condensed as reflux condensate and separated intoselected lowboiling and higher boiling fractions which are supplied,respectively, to the relatively light oil and relatively heavy oilcracking steps, the improvement which comprises subjecting fractionatedvapors of the desired end-boiling point from the aforementionedfractionating step to further fractionation whereby to separate the sameinto gasoline vapors of the desired end-boiling point and satisfactoryantiknock value and a higher boiling condensate including high-boilinggasoline fractions of unsatisfactory antiknock value, subjecting saiddesired gasoline vapors to condensation, recovering the resultingdistillate, subjecting said higher-boiling condensate to reformingconditions of cracking temperature and substantial superatmospherlcpressure in another independently controlled cracking zone, introducingregulated quantities of the highly heated products from the lastmentioned cracking zone into a coking zone to which heated residualproducts of the process are supplied as hereinafter described andwherein the latter are reduced to coke, supplying vaporous products fromthe coking zone to another low pressure separating zone, removing fromsaid zone of substantially reduced pressure said liquid componentsseparated from the vaporous components of the commingled' conversionproducts supplied thereto, introducing said liquid conversion productsinto the low pressure separating zone to which said vaporous productsfrom the coking zone are supplied, removing the resultant non-vaporousresidual liquid from said low pressure separating zone, quickly heatingthe same in another separately controlled cracking zone to a temperaturesu-fiicient to induce subsequent coking of the residual liquid,introducing the heated products from the last mentioned cracking zoneinto the coking zone wherein their high-boiling components are reducedto substantially dry coke, subjecting vaporous products from said lowpressure separating zone to fractionation for the formation of refluxcondensate, supplying the reflux condensate from the last mentionedfractionating zone to the first mentioned fractionating zone, subjectingfractionated vapors of the desired end-boiling point and comprisingmaterials within the boiling range of gasoline from said last mentionedfractionating zone to condensation, and recovering the resultingdistillate.

2. In a process for the selective cracking of relatively low-boiling[and high-boiling hydrocarbonoils wherein separate streams ofhydrocarbon oils of different boiling range characteristics are eachsubjected to conversion conditions of cracking temperature andsuperatmospheric pressure in separately controlled cracking zones, theresultant heated products commingled and subjected to appreciablecontinued cracking time at the attained temperature of the mixture andat substantial superatmospheric pressure, the resultant conversionproducts supplied in commingled state to a zone of substantially reducedpressure wherein their vaporous and liquid components separate, thevapors subjected to fractionation whereby their components boiling abovethe desired temperature are condensed as reflux condensate and separatedinto selected low-boiling and higher boiling fractions which aresupplied, respectively, to the relatively light oil and relatively heavyoil cracking steps, non-vaporous residual liquid supplied in regulatedquantities from said zone of reduced pressure to another separatecracking zone wherein it is quickly heated to an independentlycontrolled cracking temperature and the heated products introduced intoa coking zone wherein their high-boiling components are reduced to coke,the improvement which comprises removing vaporous products from thecoking zone, supplying the same to another separating zone whereinhigh-boiling components undesirable as cracking stock for either of thefirst mentioned selective cracking stages are removed therefrom,removing said high-boiling components in liquid state from the lastmentioned separating zone and supplying the latter to the same crackingzone to which said residual liquid is supplied, subjecting vaporousproducts of the coking operation from the last mentioned separating zoneto separate fractionation for the formation of reflux condensate,returning the last mentioned reflux condensate in regulated quantitiesto the first mentioned fractionating zone, subjecting fractionatedvapors of the desired end-boiling point from said separate fractionatingzone to condensation, recovering the resulting distillate, subjectingfractionated vapors of the desired end-boiling point from the r firstmentioned fractionating zone to further fractionation whereby they areseparated into gasoline vapors of the desired end-boiling point andhigher boiling condensate including heavy gasoline fractions ofunsatisfactory antiknock value, subjecting said gasoline vapors of thedesired endboiling point to condensation, recovering the resultingdistillate, subjecting said condensate including unsatisfactory gasolinefractions to reforming conditions of high cracking temperature andsubstantial superatmospheric pressure in another independentlycontrolled cracking zone, introducing regulated quantities of the highlyheated products from the last mentioned cracking zone into the cokingzone to assist the coking operation, cooling the remaining portion ofsaid highly heated products sufficiently to prevent their substantialfurther cracking, separating heavy liquid components from the partiallycooled materials,returning said heavyliquids to the same cracking zoneto which said residual liquid is supplied, subjecting vaporouscomponents of the partially cooled materials to fractionation for theformation of reflux condensate and the recovery of fractionated vaporsof the desired endto the reforming stage of the system is first passedin indirect heat exchange with reflux condensate formed in thefractionating zone to which the vaporous products of the cokingoperation are supplied, prior to the return of said reflux condensate tothe first mentioned fractionating zone. I

4. A process such as defined in claim 2 wherein at least a portion ofsaidrcondensate supplied to the reforming stage of the system is firstpassed in indirect heatvexchange with reflux condensate formed in thefractionating zone to which the vaporous products of the cokingoperation are supplied, prior to the return of said reflux condensatetothe first mentioned fractionating zone. 7

l 5. In a process wherein hydrocarbon oils are cracked at elevatedtemperature and superatmospheric pressure, the resulting vaporous andliquid conversion products "separated, the vapor fractionated to formreflux condensate which is returned to said cracking operation forfurther cracking and said liquid products appreciably further vaporizedat substantially reduced pressure relative to that employed inthecracking zone whereby additional vapors are formed, the improvementwhich comprises removing resultant non -vaporous liquid residue from thezone wherein said further vaporization of the liquid conversion productsisqaccomplishedand reducingits high-boiling components to coke in acoking zone, separating high-boiling components from the vaporousproductsof the coking operation and returning the same to the cokingzone for further treatment, recovering fractions boiling within therange of the desired gasoline product from the remaining vaporousproducts of the coking operation, condensing intermediate fractions ofthe vaporous products of the coking operation and returning the same totheaforementioned cracking operation for further cracking, saidadditional vapors being fractionated together with said remainingvaporous products of the coking operation whereby condensed portions ofthe additional vapors are also returned to the cracking operation,further fractionating the vaporous products from which said refluxcondensate has been recovered to separate therefrom. desirable gasolinefractions 'of satisfactory anti-knock value, which are condensed andrecovered, and to form a higher boiling condensate comprising heavygasolinefractions of unsatisfactory anti-knock value, subjecting saidhigher boiling condensate in a separate cracking zone to independentlycontrolled cracking conditions of elevated temperature andsuperatmospheric pressure adequate to materially improve the anti-knockvalue of said heavy gasoline fractions, recovering good anti-knockgasoline from the vaporous products -of\ the last mentioned crackingoperation, separating the remainder of the last named conversionproducts into light and heavy liquid fractions, returning the latter-tothe coking zone for further treatment and returning the former to thefirst mentioned cracking operation for further cracking.

6. A process such as defined in claim 5 wherein the first mentionedcracking operation comprises two independently controlled cracking stepsto which are selectively supplied relatively low-boiling and higherboiling fractions of said reflux condensate.

'7. A process such as defined in claim 5 wherein said fractionation ofthe first mentioned vaporous products is accomplished in commingledstate with hydrocarbon oil charging stock for the process, the resultingreflux condensate being separated into selected relatively low-boilingand higher boiling fractions, each of which contain selected fractionsof said charging stock, and wherein the first mentioned crackingoperation comprises independently controlled cracking steps to-whichsaid low-boiling and higher boil ing fractions of the reflux condensateare selectively supplied.

8, A process such as defined in claim 5 wherein non-vaporous liquidresidue resulting from initial further vaporization of the liquidproducts of the first mentioned cracking operation is introduced, priorto said coking thereof, into a zone of secondary further vaporization towhich said vaporous products of the coking operation are supplied andwherein said separation of highboiling components from the latter isaccomplished, the liquid residue from said zone of secondary furthervaporization being supplied to the coking zone.

9. A process such as defined in claim 5 wherein non-vaporous liquidresidue resulting from initial further vaporization of the liquidproducts of the first mentioned cracking operation is introduced, priorto said coking thereof, into a zone of secondary further vaporization towhich said vaporous products of the coking operation are supplied andwherein said separation of highboiling components from the latter isaccomplished, resultant liquid residue being removed from said zone ofsecondary further vaporization, quickly heated to a higher crackingtemperature in an independently controlled heating zone of the systemand the resulting highly heated products introduced into saidcoking zonewherein their high-boiling components are reduced to coke.

10. A process such as defined in claim 5 wherep in the first mentionedcracking operation comprises two independently controlled cracking stepsto which selected relatively low-boiling and higher boiling fractions ofsaid reflux condensate are selectively supplied and wherein regulatedquantities of the highly heated products from the cracking step to whichsaid relatively low-boiling fractions of the reflux condensate aresupplied, are introduced into the coking zone wherein they serve as aheating mediumfor assisting coking of said liquid residue.

11. A process such as defined in claim 5 wherein said condensedintermediate fractions of the vaporous products of the coking operationare returned to the fractionating step to which said vaporous productsof the first mentioned cracking operation are supplied, refluxcondensate resulting from said fractionation of the commingled materialsbeing separated into selected relatively low-boiling and higher boilingfractions which are selectively supplied to independently controlledlight oil and relatively heavy oil cracking steps of the first mentionedcracking operation.

12. A process such as defined in claim 5 wherein said light liquidfractions separated from said remaining conversion products of the lastmentioned cracking operation are commingled with said vaporous productsof the first mentioned cracking operation in the zone wherein the latterare fractionated, and wherein reflux condensate resulting fromfractionation of the commingled materials is separated into selectedrelatively low-boiling and higher boiling fractions which areselectively supplied to independently controlled relatively light oiland relatively heavy oil cracking steps of the first mentioned crackingoperation.

13. In a process wherein hydrocarbon oils are cracked at elevatedtemperature and superatmosplieric pressure, the resulting vaporous andliquid conversion products separated, the vapors fractionated to formreflux condensate which is returned to said cracking operation forfurther cracking and said liquid products appreciably further vaporizedat substantially reduced pressure relative to that employed in thecracking zone whereby additional vapors are formed, the improvementwhich comprises removing resultant non-vaporous liquid residue from thezone wherein said further vaporization of the liquid conversion productsis accomplished and reducing its high-boiling components to coke in acoking zone, separating high-boiling components from the vaporousproducts of the coking operation and returning the same to the cokingzone for further treatment, fractionating the remaining vaporousproducts of the coking operation in admixture with said additionalvapors but out of contact with the aforementioned vapors of the crackingoperation to form a separate reflux condensate, returning the latter tothe first mentioned fractionating step and separately recoverr inggasoline fractions from the fractionated vapors of each of saidfractionating steps, the process being further characterized in thatsaid cracking operation comprises two independently controlled crackingsteps to which selected relatively low-boiling and higher boilingfractions of the reflux condensate from the first mentionedfractionating steps are selectively supplied and in that regulatedquantities of the highly heated products from the cracking step to whichsaid relatively low-boiling fractions are supplied, are introduced intothe coking zone wherein they serve as a heating medium for assistingcoking of said liquid residue.

14. A process such as defined in claim 13 wherein non-vaporous liquidresidue resulting from initial further vaporization of the liquidproducts of said cracking operation are introduced, prior to said cokingthereof, into a zone of secondary further vaporization to which saidvaporous products of the coking operation are supplied and wherein saidseparation of highboiling components from the latter is accomplished,the liquid residue from said zone of secondary further vaporizationbeing supplied to the coking zone.

15. A process such as defined in claim 13 wherein non-vaporous liquidresidue resulting from initial further vaporization of the liquidproducts of said cracking operation are introduced, prior to said cokingthereof, into a zone of secondary further vaporization to which saidvaporous products of the coking operation are supplied and wherein saidseparation of highboiling components from the latter is accomplished,resultant liquid residue being removed from said zone of secondaryfurther vaporization, quickly heated to a high cracking temperature inan independently controlled heating zone of the system and the resultinghighly heated products introduced into said coking zone wherein theirhigh-boiling components are reduced to coke.

16. In a process wherein hydrocarbon oils are cracked at elevatedtemperature and superatmos' pheric pressure, the resulting vaporous andliquid conversion products separated, and the vapors fractionated toform reflux condensate which is returned to said cracking operation forfurther cracking, the improvement which comprises further fractionatingthe vaporous products from which said reflux condensate has beenrecovered to separate therefrom desirable gasoline fractions ofsatisfactory anti-knock value, which are con densed and recovered, andto form a higher boiling condensate comprising heavy gasoline frac-'tions of unsatisfactory anti-knock value, heating said higher boilingcondensate in a separate cracking zone to independently controlledcracking conditions of elevated temperature and superatmosphericpressure adequate to materially improve the anti-knock value of saidheavy gasoline fractions, effecting appreciable further vaporization ofsaid liquid products of the first mentioned cracking operation in a zoneof substantially re- I duo-ed pressure relative to that wherein they areformed, introducing resulting non-vaporous liquid residue and productsof the last mentioned cracking operation into another vaporizing andseparating zone wherein further vaporization of said liquid residue isaccomplished and wherein vaporous and high-boiling liquid fractions ofsaid last mentioned conversion products are separated, separatelyremoving the resulting non-vaporous residual liquid products and vaporsfrom the last mentioned vaporizing and separating zone and fractionatingthe vapors to separate therefrom desirable gasoline fractions which arecondensed and recovered, the process being further characterized in thatthe first mentioned cracking operation comprises two independentlycontrolled cracking steps to which are selectively supplied relativelylow-boiling and higher boiling fractions of the reflux condensate formedin the first mentioned fractionating step and in that reflux condensateresulting from said fractionation of the last named vapors is alsoseparated into selected relatively low-boiling and higher boilingfractions which are selectively returned for further cracking to saidindependently controlled cracking steps of the first mentioned cracking

